To the knowledge of the applicant, currently, time-honored ring spinning is still the most leading method for producing spun yarns. The method is used to draft fed fiber strands with a twist and twist them into desired spun yarns. However, the following major problems exist in ring spinning: Owing to the existence of a triangle zone, on the one hand, the head and tail of fibers are not easily wrapped into yarns to form hairiness, and on the other hand, edge fibers and central fibers are not easily broken at the same time because of a great tension difference between them so that the strength of individual fibers cannot be fully utilized and the strength of single yarns is reduced.
To solve these problems, researchers in the textile industry have made many researches on the triangle zone in ring spinning and have achieved a series of fruitful achievements in theoretical researches and engineering practice. In the searches on optimization and improvement, especially reduction or even elimination of the triangle zone in ring spinning, the airflow integration method has become an important technique to integrate drafted strands compactly.
For example, a Chinese invention patent (Patent No.: 95108623.5, authorized publication number: CN 1048298 C) discloses a spinning method and a fine spinning frame adopting a suction roller with a guider on the drafting mechanism. An air suction roller is equipped in the patent and a radial air suction zone is equipped on the exterior circumference of the air suction roller so that air flowing into the air suction roller produces a condensation action to condense crafted twistless fiber bands into compact fiber strands. Moreover, a Chinese utility model (Patent No.: 032056083, authorized publication number: CN2677396 Y) discloses a spun yarn integration spinning device adopting a short suction tube and a technique similar to that in Patent No. 95108623.5 is also adopted in Patent No. 03205608.7.
All prior airflow integration techniques adopt a negative-pressure airflow to condense drafted twistless fiber strands in the area between the output of the roller and twist so as to reduce the triangle zone, improve the quality of resultant yarns, and especially reduce the hairiness of resultant yarns. However, the action of such direct condensation upon integration and compression of fiber strands is limited after all. In addition, fiber strands cannot obtain an original twist before being twisted, which cannot help to improve the strength of final resultant yarns.